Proper grooming of grapevines renders the vines more photosynthetically active and allows greater penetration of light into the fruit zone and lower buds. Increased light in the vine improves both fruit quality and productivity. In order to provide better sun penetration, vineyards are often slightly elevated above the surrounding land or planted on sloped grounds. Furthermore, sloped grounds may provide an opportunity for cold air to drain on one or two sides. Air drainage through and away from a vineyard not only reduces the danger from late-spring and early-fall frosts, but is important in the control of many grape diseases.
It has been recognized that the vines should be pruned each year so that a controlled growth results in the next growing season to provide a desired balance between the amount of foliage growth and the amount of fruit grown on the vines. Proper pruning is a selective process of reducing bud numbers while retaining premium quality fruiting buds on vine canes. If too many buds on the vine spurs remain after the pruning, there will be an excessive number of grape bunches formed. The vine will then put a relatively large amount of its energy into producing the fruit crop and a relatively small amount of its energy into vine and foliage growth. Since each leaf of the foliage supplies nutrients and energy from the sun to the plant, too little foliage will result in the vine having insufficient energy to produce the excessive fruit crop. As a consequence, the crop will have low sugar content and poor quality.
On the other hand, if too few buds are left, too great an amount of energy of the plant will go into producing foliage and growing vines. The fruit crop will have high sugar content and high quality, but the crop amount will be small. Proper pruning that provides a balance of foliage and crop growth with fruit buds will result in a maximum harvest of high quality grapes.
In the grape industry, a significant amount of grapevine pruning is done manually with scissor-like pruning shears. This is particularly true with respect to Vitis labruscana grapes (also known as ‘Concord’ and ‘Niagra’ grapes) which exhibit a drooping vine growth habit. The drooping vine growth of Vitis labruscana grapes creates a tangled canopy of vines that makes mechanical pruning difficult. Mechanical pruners have been developed because of the costs and difficulty in obtaining adequate hand labor to accomplish manual pruning in a timely manner. These mechanical pruners, however, typically have rigid or stationary hedgers that lack the control and precision of manual pruning.